57 lines
1.5 KiB
Python
57 lines
1.5 KiB
Python
import numpy as np
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G = 6.674e-11
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def rotations(a: np.ndarray):
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a2 = np.concatenate((a, a))
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for i in range(1, len(a)):
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yield a2[i: i + len(a)]
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def n_body(pos: np.ndarray, vel: np.ndarray, mass: np.ndarray):
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for (o_pos, o_mass) in zip(rotations(pos), rotations(mass)):
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dist = o_pos - pos
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vel += G * dist * o_mass / (np.linalg.norm(dist, axis=1) ** 3)[:, np.newaxis]
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pos += vel
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def n_body_matrix(pos: np.ndarray, vel: np.ndarray, mass: np.ndarray):
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dist = np.zeros((len(pos) - 1, len(pos), 2))
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rot_mass = np.zeros((len(mass) - 1, len(mass), 1))
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pos2 = np.concatenate((pos, pos))
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mass2 = np.concatenate((mass, mass))
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for i in range(1, len(pos)):
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dist[i - 1] = pos2[i: i + len(pos)] - pos
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rot_mass[i - 1] = mass2[i: i + len(mass)]
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vel += G * np.sum(
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dist * rot_mass / (np.linalg.norm(dist, axis=2) ** 3)[:, :, np.newaxis],
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axis=0
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)
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pos += vel
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def n_body_matrix_constrained(pos: np.ndarray, vel: np.ndarray, mass: np.ndarray, close=2.):
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dist = np.zeros((len(pos) - 1, len(pos), 2))
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rot_mass = np.zeros((len(mass) - 1, len(mass), 1))
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pos2 = np.concatenate((pos, pos))
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mass2 = np.concatenate((mass, mass))
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for i in range(1, len(pos)):
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dist[i - 1] = pos2[i: i + len(pos)] - pos
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rot_mass[i - 1] = mass2[i: i + len(mass)]
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a = np.linalg.norm(dist, axis=2)
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a[a < close] = close
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vel += G * np.sum(
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dist * rot_mass / (a ** 3)[:, :, np.newaxis],
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axis=0
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)
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pos += vel
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